Influence of fill factors on the thermal blooming of array laser beams in the air

The influence of the subaperture fill factor fs and the conformal aperture fill factor fc on the thermal blooming of array laser beams in the air is studied numerically and analytically, where coherent beam combination (CBC) and incoherent beam combination (IBC) are considered. It is shown that the array laser beam with larger values of fs and fc (when fc<3) is less affected by the thermal blooming, and the array laser beam for CBC is more sensitive to the thermal blooming than that for IBC. For CBC the maximum intensity Imax is always larger than that for IBC, but for CBC the propagation efficiency JPIB is not always larger than that for IBC due to thermal blooming effect. Moreover, the optimal fill factors fc and fs for JPIB and Imax of array laser beams are also examined. The values of optimal fill factors needed to achieve the maximum of JPIB increase with increasing the beam power, but those needed to achieve the maximum of Imax are nearly independent of the beam power. In addition, the expression for the distortion parameter of array laser beams is also derived by using the analytical method, which is in agreement with numerical results.